“There’s real science behind the idea that orthotics can decrease pain,” says John D. Willson, P.T., Ph.D., a professor at East Carolina University and one of the study authors. “But the mechanisms are less clear.” It could be, as other studies suggest, that orthotics minimize lower-leg movement, reduce muscle fatigue, or somehow activate muscles in different ways.

The study also found that, despite belief to the contrary, over-pronation isn’t a clear signal that a runner will benefit from orthotics.

The thinking goes that in runners who over-pronate, if the inside of the foot is propped up, the knee and hip will fall into better alignment, thereby relieving stress and tension on the joint. The researchers suspected this was true and set out test its validity in runners with and without patellar pain.

Subjects included 40 women aged 18 to 35 running at least 10 miles a week (women are more prone to runner’s knee). Twenty were injury-free; 20 were suffering from PFPS pain and had been for at least two months.

The researchers measured each women’s “standing calcaneal angle” (an indicator of pronation amount) prior to the test to determine if any shifts in hip and knee alignment were dependent on pronation.

All runners wore the same shoes (New Balance 629) with and without the orthotics. Biomechanics were recorded using 3D motion detectors.

The results did show small but statistically significant changes to hip and knee motion, but not enough to conclude that orthotics improved biomechanics for runners with or without injury and regardless of pronation level. (The researchers note that the shift at the hip could theoretically ease strain on the iliotibial band, while changes at the knee could potentially increase strain on the joint.)

The study was the first to look at the relationship among orthotics and hip and knee mechanics during running in both injured and uninjured runners.

“There’s a need to tailor orthotic prescription based on the characteristics of the runner, and this study tells us we still have not identified the characteristics that are most telling,” says Willson.